Batteries are EVERYWHERE, we use them EVERYDAY. Yet how many people really understand them? A campervan without batteries or electrics is... well, just a tin can. In this article, we are going deep on deep cycle leisure batteries. We will look at the different types of leisure batteries (AGM, FLA, gel, and lithium ion leisure batteries), how to install leisure batteries in your van conversion, how to calculate the size of the battery, the best leisure batteries on the market, the lifespan you can expect from your batteries and how you can maximise that lifespan, and much more! By the end you will have a very thorough understanding leisure batteries and be ready for your own electrical installation!
I'm Shane, I've been teaching people to convert campervans for many years, I'm the author of The Van Conversion Newsletter, the van conversion instructor at Udemy, and the proud owner of a beautiful self-build campervan called Beans. So let's jump in and have a look at leisure batteries for van conversions!
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Index
Types of leisure batteries (Lead-acid, AGM, Gel, Lithium, Lead-crystal)
How to calculate the size of leisure batteries for your van conversion
How long does it take to charge leisure batteries (solar panels, split charge relay, shore power)?
Note: Before we hop in, you might want to grab yourself a wiring diagram which you can get for free by signing up to The Van Conversion Newsletter (suggested, but not mandatory 🙂 - wiring diagram gets sent to you straight away).
Supplies list 🛒
Note: Whilst a lithium leisure battery is preferable, I understand it is rather expensive! As a cheaper alternative, you could get a 200Ah AGM battery instead.
 | Common connection point for positive and negative cables |
 | Leisure battery kill switch |
 | Protects the leisure battery in case of surge |
 | For monitoring the levels/health of your leisure batteries |
 | Leisure battery terminal connectors For connecting cable to your leisure battery |
What are leisure batteries?
A battery is a device that stores chemical energy, and converts it to electricity on demand. This is known as electrochemistry. To put it more simply: electricity is stored in batteries. Campervans are powered by leisure batteries - batteries which provide a steady flow of current over a prolonged period. Leisure batteries for van conversions are typically 12v and are used to power everything from the fan and fridge to heater and lights. Leisure batteries are also known as deep cycle leisure batteries, they are designed for repetitive, deeper discharges and last a long time.
Starter batteries vs. deep cycle leisure batteries
A starter (cranking) battery is what kicks your van into action when you turn the ignition. Starter batteries are designed to provide a big burst of energy (which the starter motor needs), the energy is supplied fast and can use as much as 20% of their total capacity per start. Once the engine starts up, the alternator recharges the starter battery so it’s ready to go for the next time you start up.
Deep-cycle leisure batteries in contrast release energy in a steady flow over a longer period - as mentioned above. They are designed to withstand hundreds/thousands of charging cycles.
The anatomy of deep cycle leisure batteries (complex, so feel free to skip this section if you like 🙂)
A deep cycle leisure battery is a plastic container, typically with six individual compartments inside.
Each compartment creates 2.12 Volts, therefore creating 12.7V in total for a fully-charged battery.
Each compartment contains rows of positive and negative lead plates. These are setup in a grid so that lead oxide paste can be squeezed into all the little openings. Each plate is erected in a perforated piece of plastic called a separator.
In a deep cycle leisure battery, these plates are thicker than in starter batteries; the separators also contain glass fibre sheets to squish against the lead oxide paste.
The glass fibre sheets help protect the batteries during constant re-charging (the paste can become loose and then completely come off from the lead grid).
The compartments of lead-acid batteries are filled with sulphuric acid (so be careful with these things!). Consequently, the plastic casing has a gas outlet for releasing hydrogen created during recharging. Though sealed lead-acid batteries do not have this outlet. Similarly, lithium batteries do not need to worry about any sulphuric acid.
Depth of discharge and battery cycles
Deep cycle leisure batteries are designed to discharge power at a slow, steady rate over a long period of time. They are known as deep cycle batteries.
Leisure batteries can be discharged to a certain level, known as it's depth of discharge (DOD), hundreds/thousands of times in their lifetime.
A single discharge is known as a cycle. Lead acid batteries can (should) typically be discharged to 50%, whereas lithium batteries can be discharged far more (to about 80%)
We should be cautious never to completely drain our leisure batteries, and certainly never leave a battery in a completely discharged state. If recharging is delayed, sulfonation occurs. During sulfonation a white deposit forms on the battery’s plates. This is incurable and renders the battery useless.
Sometimes when sulfonation occurs the lead plates inside the batteries can fall over. When this happens you will see that the battery voltage falls to weird levels like 8v or lower. This is NOT normal, a deep cycle leisure battery should never be able fall below ~11v.
It is possible to bring a battery back from an event like this by charging it up (typically with a very heavy charge initially). However, the more you allow your batteries to fall flat, the worse sulfonation will get until the batteries are rendered useless.
Take good care of your batteries and your batteries will take good care of you 😇.
Types of leisure batteries (Lead-acid, AGM, Gel, Lithium, Lead-crystal)
At the highest level, there are two types of deep cycle leisure batteries:
1. Lead-acid batteries
2. Lithium (LiFeP04) batteries
Lead-acid batteries
Lead-acid batteries are broken down into two subcategories:
a. Flooded (open/wet) lead-acid batteries
b. Sealed (VRLA) lead-acid batteries
Flooded lead-acid batteries emit gas (hydrogen) and thus need to be adequately ventilated. Occasionally they will need to be refilled with deionised water and must be kept securely upright! They are usually very cheap, but I do not recommend flooded lead-acid batteries for van conversions. They normally have a lifespan of 4-8 years with regular maintenance.
Note: If the batteries are overcharged they can emit sulphuric gas.
Sealed lead-acid batteries are sealed, thus they do not need any ventilation. Similarly, they do not need any topping up with deionised water. I recommend sealed lead-acid (or lithium) batteries for van conversions.
If we dive just a little deeper into sealed lead-acid leisure batteries, we find that we have two types:
i. AGM leisure batteries (Absorbed glass mat)
ii. Gel leisure batteries
AGM leisure batteries are the cheapest type of sealed lead-acid battery. They are rugged and require no maintenance. They also charge well off solar power. They are the most popular type of battery for van conversions. They have a longer life than flooded lead-acid batteries and work better in colder conditions. Interestingly, AGM leisure batteries can be used as starter batteries as well as leisure batteries. You can expect to get roughly 500 charge cycles (at 50% DOD) from an AGM leisure battery.
Note: When recharging an AGM leisure battery, the charge voltage must not exceed 14.4v (A battery charger or solar charge controller will handle this for you).
Gel leisure batteries have all the benefits of AGM leisure batteries but with a longer life (if they are cared for!). However they are incredibly heavy. Gel leisure batteries operate better in warmer and colder climates than AGM leisure batteries. You can expect to get roughly 1000 charge cycles (at 50% DOD) from a gel leisure battery.
Note: When recharging an Gel leisure battery, the charge voltage must not exceed 14.2v.
How long do leisure batteries last?
Flooded lead acid normally have a lifespan of 4-8 years with regular maintenance.
AGM leisure batteries typically have 500 charge cycles (at 50% DOD).
Gel leisure batteries typically have 1000 charge cycles (at 50% DOD).
Lithium ion leisure batteries typically get upwards of 1500 charging cycles (no limit on DOD).
As a rough rule of thumb, gel leisure batteries have twice as many charge cycles as AGM leisure batteries. Check out this graph below (super interesting 🤓). If we are careless with our batteries and discharge them 80-100% we absolutely destroy the lifespan of the battery (in both cases). In contrast, if we are kind to our batteries and only discharge them 25% our batteries will last a hell of a lot longer!
Keep those batteries charged boys and girls!
Lithium ion leisure batteries (LiFeP04)
I won't beat around the bush, lithium ion leisure batteries are awesome. Lithium ion leisure batteries provide as much energy as lead-acid batteries for a quarter the weight and smaller size! 🤯 The lifespan (number of charge cycles) of a Lithium ion leisure batteries is up to 5+ times that of a lead-acid battery and has a depth of discharge of 80%.
There is no liquid in Lithium ion leisure batteries so they can even be mounted upside-down. They require little maintenance and charge much faster than lead acid batteries.
Surely there's a catch? Yep 😢 The pricetag. They are up to four times the price of a lead-acid battery. However in this van converter's humble opinion: well worth the price. Only recently, I removed four sealed lead-acid batteries (520Ah) from my van and replaced them with a single 200Ah lithium ion leisure battery; and I couldn't be happier.
Given the graph below, with a DOD of 50%, we can expect to get ~1150 charge cycles from our Lithium ion leisure batteries. Though, with high quality Lithium ion leisure batteries you can expect 2000-4000 charge cycles.
It's worth noting that Lithium ion leisure batteries function worse in very cold temperatures when compared to lead-acid.
One last thing that is important to note about lithium batteries is that you must use a DC-DC battery charger when split charging them; you cannot use a voltage sensitive relay. Related guide: Split charging campervans.
Lead-crystal batteries
I'm going to give these rarer batteries an honorable mention. They are not popular in van conversions yet because they are relatively new. They also have no liquid meaning there is no risk of spillage or sulfonation. They were originally designed by UPS and are around twice the price of a regular lead-acid battery.
Lead-crystal batteries charge twice as quick a lead-acid, have more charge cycles, and appealingly can function in very extreme temperatures.
Categories (class) of leisure battery
A leisure battery is certified class A, B, or C. A lasts the longest and is designed for frequent use, C lastest the shortest length of time and is designed for infrequent use. A has more lead, C has less lead.
Category A is for higher storage capacity for people who frequently use their campervans away from electrical hook-ups
Category B are aimed at those who frequently use sites with hook-up facilities, but require a greater battery capacity.
Category C is for users that require a lower capacity battery, just to cover basic operation of their appliances for short periods away from a hook-up
It is worth pointing out that Category A batteries will be significantly heavier than their C Counterpart. Weight is a good measure of quality with lead-acid batteries; the heavier, the better.
I would suggest you grab yourself a nice, heavy category A leisure battery (or a Lithium ion leisure battery).
Charging profiles of deep cycle leisure batteries
Charging profiles of deep cycle leisure batteries normally follow three stages: bulk, absorption and float. The charging limits differ between the different battery types.
Bulk: a fast, constant current charge up to ~80% State of Charge (SoC)
Absorption: much slower, constant voltage charge to reach 100% SoC
Float: a constant voltage charge which maintains 100% SoC by counteracting self-discharge
Note how different batteries charge best at different voltages. Lead-acid batteries (AGM, Gel, FLA) in particular require large voltages in the bulk and absorption stages of the charge profile. Lithium ion leisure batteries are the inverse - they require less power initially and gradually ramp up.
It is also worth pointing out that the current (amperage) works in the opposite way - at the beginning of the charge profile, the amperage starts high and gradually gets lower.
A solar charge controller or battery charger ensures that the voltage and amperage matches the charge stage of the battery. It is paramount that is does its job correctly. For example, if we had four solar panels wired in series (74.4v) wired directly to our leisure batteries, we could be in for a very, very dangerous time indeed. The sulphuric acid will begin to boil and the plastic casing will start to melt... 😲
How to maximise the life of your deep cycle leisure batteries
MOST IMPORTANT: Keep your batteries nice and charged up (>50%) to increase the number of charge cycles.
NEVER let your batteries remain fully uncharged or you risk sulfonation which is an incurable disease for batteries.
Before mounting terminal clamps on the battery terminals, apply a thin layer of Vaseline to the battery’s terminals.
If you’re not currently using your campervan, make sure you use a trickle charger (keep it plugged into mains) to stop the leisure battery from completely losing charge.
If you are using flooded lead-acid batteries, make sure you regularly check that the electrolyte level covers the lead plates on the battery. If it doesn’t, make sure you top it up with deionised water.
Every now and then check that the gas relief tube is fitted securely.
Factors affecting the performance of leisure batteries
Temperature: The colder the temperature, the poorer the performance of the battery. The Ah rating stated on a battery is based on a temperature of 25C, with each degree lower causing a 1% drop in performance. For example, an 110Ah battery operating in 15C temperature will actually perform as a 100Ah.
Age: Most leisure batteries will not last more than ~five years and experience a decrease in performance over time.
Power consumption: If a large number of appliances (high wattage) are run from the leisure battery, it will discharge quicker and therefore need to be recharged more often. This frequent recharging will cause the battery to degrade sooner.
Category: As mentioned before, Category B and C batteries will not last as long as Category A batteries due to their being less lead in the battery.
How to calculate the size of deep cycle leisure batteries for your camper van
Quick note: For an in-depth explanation of electricity as it relates to van conversions (Volts, Amps, Watts, Fuses, Wire sizes, AC/DC, Solar, batteries), I highly suggest you check out this complete guide. Below, I will give an overview of what is covered in that article.
To calculate our battery size we will be filling out a load sheet that looks like the image below. You can download a blank template of this load worksheet here.
In order to figure out the size our leisure batteries need to be, we will first need to figure out all the appliances we will have in our campervan. List out all the electrical appliances you want in your van in the worksheet.
Enter the quantity you will have of each item.
Enter the Voltage of the appliances; most appliances will be 12v DC, though some will be 230v AC (eg. the laptop is charged through the mains plug sockets).
Enter the Amps of each individual appliance (you can find this on the spec sheet for the appliance)
Total amps will auto populate (quantity X amps)
Watts will auto populate (Total Amps X Volts)
Enter the number of hours per day you estimate you will use the appliance (Note: fridges turn on and off throughout the day, so you don't need to enter 24 hours for your fridge)
Total watt hours will automatically be populated for you.
The output at the very bottom of this worksheet is the total watt hours (Wh) that will be used given all our appliances.
We will quickly convert the Watt hours (Wh) to Amp hours (Ah) as Ah is more commonly used for sizing 12v leisure batteries.
The formula to convert Wh to Ah is: Ah = Wh / V
So given our estimated loads, Ah = 1185Wh / 12. Which gives us ~98Ah
In other words, we can expect to use 98Ah of battery power per day in our campervan. However I want to be able to be off-grid for at least two days, so I'm going to multiply the Ah by two to give me 196Ah.
One further caveat; remember we can only discharge lead-acid batteries to 50%, so we will actually need TWICE our calculated Ah. 2 X 196Ah = 392Ah. Hence the reason why I had 520Ah of battery power up until recently.
How long does it take to charge leisure batteries (solar panels, split charge relay, shore power)?
There are three ways of charging leisure batteries in a campervan:
Split charge relay (connect to the alternator of the vehicle so you charge up while driving)
Shore power (plug into mains)
So, let's figure out how long it will take to recharge our leisure batteries with solar panels, a split charge relay, or shore power.
Battery size
Let’s say for argument's sake we have 392Ah of leisure battery storage. We can discharge it 50% and so we will need to fill 196Ah. Let's quickly convert this back to Wh for ease of calculation. The formula is Wh = Ah * V, which would give us 2304Wh.
Battery efficiency: Lithium batteries charge at nearly 100% efficiency, compared to the 85% efficiency of most lead acid batteries. This is due to their charging profiles. The charging efficiency of lead acid batteries gets particularly bad when they are discharged more than 50%.
Ambient temperature also has a big effect on the charging efficiency of batteries; colder temperatures lower efficiency a lot.
C-rating: A battery’s charge (and discharge) rate is controlled by its C-rating. The C-rating of a leisure battery describes the fastest possible time it takes to charge or discharge said battery.
The C-rating of a lead acid battery is 0.2C, whereas the C-rating of a lithium leisure battery is typically 0.5C. Accordingly, given the following table, the fastest we could ever charge a lead acid battery from empty is 5 hours (2.5 hours from 50% DOD). The fastest we could ever charge a lithium leisure battery is 2 hours (1 hour from 50% DOD).
